1. Field of the Invention
The present invention relates to angular rate measuring devices-rate gyroscopes, and more particularly, to such an angular rate measuring device having an unsymmetrical rotor producing Coriolis forces, and a gimbal tuned to increase sensitivity to such forces for measuring the angular rate of movement of a vehicle about a given axis.
2. Description of the Prior Art
A conventional, free-mounted gyroscope consisting of a rotor which is caused to spin at high speed upon its axle within a gimbal system providing freedom for rotation about each of two mutually perpendicular axes, each perpendicular to the axis of rotation of the rotor, will be caused to precess solely by reason of movement of the gyroscope in space only if the rotor is perfectly balanced and if each of the respective gimbal axes passes precisely through the center of gravity of the rotor and gimbal system. As a significant rate of precession may be caused by a minute displacement of the rotor axle along its bearings, the inevitable errors in manufacture of conventional designs are sufficient to make the gyroscope wander to an extent which imposes fundamental limits on its use as a navigational instrument, particularly in view of the large and sudden accelerations to which the gyroscope is subjected when it is mounted in an aircraft or missile.
Reduction in steady-state null errors by the use of a vibrating rotor gyroscope was demonstrated in: U.S. Pat. No. 1,801,619 - Arrea, U.S. Pat. No. 3,382,726 - Erdley, and U.s. Pat. No. 3,463,016 - Erdley et al. An unsymmetrical rotor, as shown in U.S. Pat. No. 2,991,659 - Bowden and in U.S. Pat. No. 3,191,445 - Eklund, is capable of producing vibratory signals at twice the rotor frequency. These signals, however, must be separated from spin bearing noise which is considered to be a principal source of error.
In flight-critical systems where multiple redundant components are required, a low-cost gyroscope is essential. Ideally, therefore, simplification of the mechanical configuration of the gyroscope is desirable to achieve a cost saving. However, cost saving must not be achieved at the expense of good null stability, since this error is not predictable and cannot be corrected. Predictable errors such as g-sensitivity, non-linearities, etc. can be compensated for, by the use of electronics.
Accordingly, it is an object of the present invention to produce a mechanically simplified angular rate measuring device-gyroscope.
It is a further object of this invention to produce such a mechanically simplified gyroscope but which lacks the major sources of null instability, including: gimbal imbalance, flotation errors, and steady-state gimbal torques.